1. Field of the Invention
The present invention relates to an optical connector plug and an optical connector for holding a front end of an optical fiber and optically connecting the optical fibers.
2. Description of the Related Art
Conventionally, optical connection of optical fibers used in optical communication or the like is carried out by a method of using an optical connector having an optical connector plug holding a front end of the optical fiber and an optical connector adapter for carrying out optical connection of the optical fibers by fixing the optical connector plugs, or a method of fusion-welding front end faces of the optical fibers.
According to the optical connection of the optical fibers by fusion-welding, there arises a problem that attachment and detachment of the optical connection of the optical fibers cannot be carried out. There also arises a problem that fusion-welding steps are complicated which gives rise to a problem that there is a restriction in use thereof.
Therefore, by using an SC type optical connector using a cylindrical member for a ferrule which holds an optical fiber and has an outer diameter of 2.5 mm, or a comparatively downsized MU type optical connector using a cylindrical member for a ferrule which holds an optical fiber and has an outer diameter of 1.25 mm, or the like, the optical fiber fusion-welding steps are unnecessary, and attachment and detachment of the optical connection of the optical fibers is easily carried out.
Optical fibers have lately been applied to access networks that connect subscribers' lines to telephone switching stations. This is called Fiber To The Home (FTTH) and can build a high-speed communication environment. Optical fiber communications use in general infrared rays having a wavelength of 1.3 to 1.55 μm, but a steady increase in output power is being observed.
A protective cover has been proposed to protect the front end face of an optical fiber from contaminants such as dust, finger prints, and water spots (see JP07-281055 A and JP2002-156557 A, for example) The cover is placed along the outer circumference of an optical connector plug that holds the optical fiber, and is operated to cover the front end face of the optical connector plug.
A problem of any SC type, MU type, or like other conventional optical connector plug is that light is radiated from the front end face of an optical fiber it holds since the light could be hazardous to human health if radiated for a certain period of time onto human body, especially a localized area such as an eye.
While a particularly high level of safety is required of an optical connector plug that holds the tip of an optical fiber that is led inside a house by FTTH or the like, common SC type, MU type, or other optical connector plugs currently used in FTTH have no preventive measures against light radiation and accordingly contain a hazard to health.
The risk of harming human body with light irradiated from the tip of an optical fiber is increasing with the increase in output power of optical communications.
The cover provided to protect the front end face of an optical fiber in the optical connector plug that is disclosed in JP 07-281055 A and JP 2002-156557 A mentioned above can also block light radiated from the tip of the optical fiber. However, a drawback of the optical connector plug having a cover is that the cover, which is placed and operated on an outer wall of the optical connector plug, gives the optical connector plug contours different from those of conventional optical connector plugs. The unusually shaped optical connector plug makes it necessary for an optical connector adapter, which connects two optical connector plugs with each other face-to-face, to have a shape different from its conventional shape in conformity with the unique shape of the optical connector plug, thereby raising the manufacture cost.
The optical connector plug having a cover also requires a new specification separate from the existing one for SC type, MU type, and other conventional optical connector plugs, meaning that it is incompatible with SC type, MU type, and other conventional optical connector plugs. In order to apply the optical connector plug having a cover and the new specification to existing equipment where an SC type or MU type optical connector plug has been employed, every component of the equipment has to be replaced with new one at high cost.